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[cuttinhorse]

I had to put 1/2 a tank of mid grade in the 08 SERK the other day because the startion was out of premium and I didn't think I would make it to the next station. The engine light came on and off after that. I havn't had a chance to ride since then and fill with premium but am wondering if mid grade could throw a code for per detonation or something?

[mr_magoo]

Wouldn't think the fuel would trip the engine light(I use mid grade fuel all the time) take it to the dealer and have them check the code (it's stored for 50 cycles of the ignition)may just be a coincedental.

[FUZZNUTS]

On my last trip to Maggie Valley 87 octane was all that was avalible. I was told to bring Octane booster. But with all the gas stops I had there,I know I did not add the booster a few times.  I experienced no detonation, no backfire, no ill effects. And scince I had the wealth of all that CVO knowledge at MV, I posed the question. Why do we have to run high test or min 91 octane recommended by the MoCo. The general concensus was unless you run a very high compression motor.......aka worked to the nuts.......87 or 89 will not hurt anything.....I did go back to 93 octane once I reached rt 81 on the way home.   

[erniezap]

Must be nice to get 93 octane.  Out here in CA the stations only sell 91...

[Diesel Dragon]

You run a higher octane fuel to get more performance out of the engine.

You can run a lower octane but if the computer hears pre-ignition it will retard the spark timing to get rid of the pre-ignition which in turn will lower your performance.

If you have a heavy bike or a bike loaded with 2 up and gear, or like to drive it to the limit then the higher octane is a +

If your just cruising around on the highway or "driving normally" then the lower octane is fine since you probally won't put a heavy load on the engine to cause the pre-ignition in the first place.

The time before computers and knock sensors the pre-ignition could cause some major engine damage if it went on uncontrolled but with the computers and sensors the engine knows to self preserve itself, up to a point anyway.

DD

.

[FUZZNUTS]

I heard that the South West folks can't even get 91 octane.....................Mostly 89............My buddy went to Sturgis and he carried the octane booster...........89 is all he could get. Being on the east coast we're pretty lucky so far............no shortages.  

[FUZZNUTS]

My SERK dos'nt have a knock sensor.............2003............I don't know what year that started.

[Twolanerider]

I had to put 1/2 a tank of mid grade in the 08 SERK the other day because the startion was out of premium and I didn't think I would make it to the next station. The engine light came on and off after that. I havn't had a chance to ride since then and fill with premium but am wondering if mid grade could throw a code for per detonation or something?

Your fuel didn't directly cause what you're describing.  Or at least it didn't if it was what it was supposed to be. 

If it happened immediately following the fuel stop it's either an unfortunate coincidence or you got a bad load of fuel (water in a tank perhaps).

[Twolanerider]

My SERK dos'nt have a knock sensor.............2003............I don't know what year that started.

Not a part separate by itself.  Ion sensor built in to the coil and working with through the plugs and wires.

[FUZZNUTS]

Not a part separate by itself.  Ion sensor built in to the coil and working with through the plugs and wires.

Is it on my year bike?..................

[1Joker]

Bad load of fuel is what I was thinking also.

[Twolanerider]

Is it on my year bike?..................

Sure is Fuzz.

[ultrafxr]

I heard that the South West folks can't even get 91 octane.....................Mostly 89............My buddy went to Sturgis and he carried the octane booster...........89 is all he could get. Being on the east coast we're pretty lucky so far............no shortages.  

91 is what the moco recommends I think.  Here can't get 91 - either 89 or 93.  In the mountains it is my understanding that you can successfully run lower octane fuel so it is common not to find the higher octanes there.  As others have said I've never had a problem because the engine management system probably takes care of everything but I do run whatever the highest grade I can find and has never been lower than 89. 

[hogasm]

Running even 87 octane would not cause the engine light to come on without you noticing the engine spark knocking so that you would notice it.

Would bet that one of the sensors or a spark plug wire.

[grc]

I had to put 1/2 a tank of mid grade in the 08 SERK the other day because the startion was out of premium and I didn't think I would make it to the next station. The engine light came on and off after that. I havn't had a chance to ride since then and fill with premium but am wondering if mid grade could throw a code for per detonation or something?

Unless they added a DTC for the '07 and later models that I don't know about, there isn't a code for detonation.  There is a code for misfire, however, P1357 for front cylinder and P1358 for rear.  The octane level of the fuel wouldn't create a misfire, but water or dirt in the fuel could.  If your check engine light was caused by this fuel stop, I'm betting on contamination causing a misfire.

There is a way to figure this out without a trip to the dealer.  You can read the DTC's on your speedometer by placing it in diagnostic mode.  There is a post in the sticky threads with the instructions on how to access and read the codes.

Jerry


Try this link for the sticky thread:
http://www.cvoharley.com/smf/index.php?topic=6462.msg92667#msg92667